Almost every cell in the body is equipped with a membrane bound, finger-like projection called a primary cilium. Cilia have been equated to cellular antennae that detect molecular signals in the environment and thus influence how cells behave. Ciliary defects, referred to as ciliopathies, are associated with a broad spectrum of human diseases. A significant number of ciliopathies affect the craniofacial complex: Herein. I vvill investigate how cilia function during the development of the precursor cells of the craniofacial skeleton, the cranial neural crest. After mapping the presence of primary cilia on neural crest cells during distinct phases of development, I will exploit the robust avian genetic model of primary cilia disruption, the talpid. Using the Talpid I will evaluate the ability of cranial neural crest cells without primary cilia to transition from an epithelial cell to a mesenchymal cell, to migrate, to proliferate, and to form mesenchymal condensations. Finally, I will determine if primary cilia direct neural crest migration by chemotaxis. Taken together these experiments will precisely dissect hovv the primary cilia direct the development of neural crest cells; IVIy immediate goal remains the same as originally stated: to preGisely define the role of primary cilia in neural Crest development using an avian model system- To this end, the sisope of the ROO portion of the proposal is identical to the original K99. The alterations to the proposal come in the form of techniques and reagents used to accomplish the specific aims. Changes were introduced in response to pilot experiments that exposed the technical limitations of the originally proposed methodology. For example, one antibody (Arl13b) proposed to mark the ciliary axoneme does not work in an avian model system. To circumvent this problem, I engineered a ciliary reporter construct during the K99 phase of the grant. If this construct proves functional, it \N\\\ replace the previously listed antibodies as a ciliary marker Additional changes come in the form of different antibodies used for marking neural crest cells and different medlas used to culture neural crest cells. My original long-term goal was to establish an independent research program to study craniofacial patterning and during the K99 portion of funding, I accepted an offer for an Assistant Professor position at the Cincinnati Children's Hospital Medical Center (CCHMC). Therefore, the remainder of these experiments will be performed in the rich academic environment of CCHMC in Departments Of Plastic Surgery and pevelopmental Biology.